Supercharged four stroke internal combustion engine

ABSTRACT

In a four-stroke multicylinder internal combustion engine the exhaust space of each cylinder is connected to the intake of another cylinder out of phase with respect to the first by a half-cycle period via a communication pipe provided wwth nonreturn means. The underpressure due to the initial puff supercharges the second cylinder. Non-symmetrical nozzles constituting non-return means are provided in the exhaust space of each cylinder downstream of the mouth of the pipe in this exhaust space and in the intake space of each cylinder upstream of the position where the pipe opens into this intake space. Other non-return nozzles are arranged in the communication pipes. Each nozzle located in the exhaust space comprises an axial element having substantial thermal inertia and the pipe directs onto that element a flow of a fuel-air mixture having an adjustable air content, thereby reducing the atmospheric pollution. For increased efficiency, the nozzles may limit an annulus struck by the back flow and in which are provided inclined fins which cause rotation of said gas around the axis of this nozzle and prevent back flow from occuring. The invention is suitable for use in reciprocal piston and rotary piston engines.

Pouit [451 Apr. 2, 1974 SUPERCHARGED FOUR STROKE INTERNAL COMBUSTION ENGINE [76] inventor: Robert Jean Pouit, 3, rue August Mayet, 92 Asnieres, France [22] Filed: Mar. 22, 1972 [21] Appl. No.: 237,104

Related US. Application Data [63] Continuation-impart of Ser. No. 160,377, July 7,

1971, abandoned.

[30] Foreign Application Priority Data Nov. 5, 1971 France; 71.39840 [52] US. Cl 123/119 C, 6 0/901, 123/56 A,

123/59 BM I [51] Int. Cl. F02b 33/00 [58] Field of Search. 123/119 C, 119 A, 56, 59 BM, 123/59 EC, 60/901, 316, 323

[56] References Cited UNITED STATES PATENTS 2,110,986 3/1938 Kadenacy 60/324 2,297,910 10/1942 Neuland 123/119 C 3,580,232 5/1971 Sarto 123/119 A 2,198,730 4/1940 Kadenacy 60/324 2,131,957 10/1938 Kadenacy '123/65 1 2,206,193 7/1940 Kadenacy 60/324 Primary ExaminerC. J. l-lusar Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb &

Soffen [57] ABSTRACT In a four-stroke multicylinder internal combustion engine the exhaust space of each cylinder is connected to the intake of another cylinder out of phase with respect to the first by a half-cycle period via a communication pipe provided wwth non-return means. The underpressure due to the initial puff supercharges the second cylinder. Non-symmetrical nozzles constituting non-return means are provided in the exhaust space of each cylinder downstream of the mouth of the pipe in this exhaust space and in the intake space of each cylinder upstream of the position where the pipe opens into this intake space. Other non-return nozzles are arranged in the communication pipes. Each nozzle located in the exhaust space comprises an axial element having substantial thermal inertia and the pipe directs onto that element a flow of a fuel-air mixture having an adjustable air content, thereby reducing the atmospheric pollution. For increased efficiency, the nozzles may limit an annulus struck by the back flow and in which are provided inclined fins which cause rotation of said gas around the axis of this nozzle and prevent back flow from occuring. The invention is suitable for use in reciprocal piston and rotary piston engines.

25 Claims, 13 Drawing Figures PAIENTEDAPR 2:914 $800,763

sum 3 er 5 w ('0) 153 j EH9 "MENIEH APR 2 i974 SHEU k [If 5 PATENIEDAPR 2 mm 3800 763 sum 5 nr 5 SUPERCHARGED FOUR STROKE INTERN COMBUSTION ENGINE The present application is a continuation-in-part of Ser. No. 160,377 filed July 7, 1971, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to supercharged multicylinder internal combustion engines operating on a four-stroke cycle and which are less polluting then conventional internal combustion engines.

The exhaust process in internal combustion engines is an oscillatory phenomenon due to the fact that, on the opening of the exhaust ports, supersonic expansion at very high velocity of the gases constituting the first puff" or rush of gas creates behind it an underpressure in the engine cylinders. This vacuum or underpressure draws the gases contained in the exhaust passage back towards the cylinder, then the gases are again expelled, after a series of alternations clamped by friction, at the expense of power and of yield.

Attempts have already been made to avoid the return of gases after their first expulsion by supersonic expansion; mechanical or aerodynamic means have been used to oppose the return of the gases.

The vacuum generated by the exhaust of the puff, on the opening of the exhaust ports, has been used in twostroke engines to supercharge the said engines. Due to the quasi-simultaneity of opening of the exhaust and intake ports, the underpressure at the exhaust draws air or air mixed with fuel through the intake ports. The situation is fairly different in four-stroke engines. Since intake takes place at a time which is out of phase by one stroke (or by a quarter of cycle) with respect to the exhaust, up to now it has not been possible to use the underpressure created in the exhaust by the first puff in order to supercharge the engine.

SUMMARY OF THE INVENTION It is an object of the invention to increase the power and yield of multicylinder four-stroke engines by using the underpressure due to exhaust for supercharging the engine.

It is another object of the invention to provide a multicylinder internal combustion engine which runs cleaner than the conventional engines and delivers a minimum of unburnt fuel to atmosphere under normal operating conditions. For this purpose, the underpressure which exists in the exhaust space of one of the cylinders, particularly following the first exhaust puff, is made to act on the intake of another cylinder which is out of phase with respect to the first by a half-cycle.

The exhaust space of a first cylinder is communicated with the intake space of a second cylinder out of phase by a half-cycle period with respect to the first cylinder; non-return means are provided in the exhaust space of the first cylinder downstream of the mouth of the said communicating passage in this space and in the intake space of the second cylinder upstream of the place where the communicating passage opens into this intake space; said non-return means may preferably be a non-return aerodynamic nozzle, that is a nozzle which is so shaped in the direction of How that the head loss impressed to a gas flow in one direction is very much in excess of the head loss in the opposite direction. The latter head loss may even be so low as not to be significant. The nozzle may consist of an axial element of appropriate shape retained in a bulged portion of a passage. Its non-return action may be increased by giving to the axially located element and passage wall a shape and relative location such that the return gases are received in a toroidal cavity or annular recess in which they are caused to swirl. Inclined finsor blades carried by the axial element and/or wall may be used to induce rotation of the gases. There can be a first or inner group of fins which is surrounded by fins inclined in reverse direction and which form an outer group, the two groups leaving a free passage for the direct flow of exhaust gases.

It has been found that an engine according to the invention, not only has an increased power and yield, but also runs cleaner than prior art engines. More precisely, the CO content of the exhaust gases is decreased to such a point that it is negligible, as well as that of nitrogen oxides (NO),.

The unburnt hydrocarbons content of the exhaust gases is also substantially lowered.

The reduction in air pollution is all the more important if additional air is introduced into the communication pipe for the mixture to have an excess content of air. There is a strong probability that the increased reduction in pollution is due to the fact that the fuel which is projected onto the hot axial element is easily burnt and helps in resulting in a more complete combustion of all combustible contaminants in addition to the fuel itself. An important factor can also consist in the swirls which are created by the axial element.

A non-return valve may also be provided in the communication pipe for positive closure of that pipe under operating conditions for which the efficiency of the aerodynamic nozzle is not sufficient. The weight of the valve and the resilient force exerted by its return spring are preferably so proportioned that the valve remains in its open condition as soon as the speed of the engine is sufficient for the aerodynamic non-return nozzle to be efficient.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more fully understood, preferred embodiments thereof will now be described by way of illustrative and non-limiting examples, with reference to the accompanying drawings, in which:

FIG. 1 is a simplified longitudinal cross-section of a four-stroke engine with two opposite cylinders called flat twin, embodying the invention;

FIGS. 2 and 3 are diagrams explaining the operation of the engine;

FIG. 4a is a fragmentary side sectional view of the cylinder head of an engine cylinder according to the invention and including a secondary distributor;

FIGS. 4b and 40 show other positions of the secondary distributor of FIG. 4a;

FIGS. 5a and 5b are, respectively, an axial section and a fragmentary plan view of a non-return nozzle according to the invention;

FIG. 6, similar to FIG. 1, is a schematic longitudinal section of a two cylinder flat twin engine according to another embodiment of the invention;

FIG. 7 is an enlarged sectional view of means according to the invention included in the engine of FIG. 6;

FIG. 8 is a schematic view illustrating the device used for controllingair flow into the communication pipe;

FIG. 9 is a schematic cross-sectional view along line IX-IX of FIG. 10, illustrating a four-stroke rotary engine having two rotors, according to still another embodiment of the invention;

FIG. is a plane view of FIG. 9 from above.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a flat twin engine which includes two opposed cylinders 1 and 1 The pistons have inverse symmetrical movements and are coupled by rods (whose axes only are indicated) to a crankshaft 2 with two cranks 9 and9 Distribution of the four cyclic periods in the two cylinders 1 and 1 is as follows:

Cylinder l,Power-Stroke(Expansion)ExhaustIntake-Compression Cylinder l IntakeCompressionExpansion- Exhaust The diagram of FIG. 2 indicates, on a circle, the intake time of cylinder 1, (in dotted lines) and the exhaust time of cylinder 1 (in solid lines). The reference points marked on this diagram are:

AOA-Intake opening advance-RFA-Intake closing retard ACE-Exhaust opening advance-RFE-Exhaust closing retard.

Since the general arrangement of flat twin engines is well-known, it is deemed unnecessary to give a detailed description thereof. According to the invention, nonreturn nozzles (one of which 4 is shown on FIG. 1) are provided one in each of the exhaust ports 3, and 3 Similar nozzles 6 are provided in the intake ports 5, and 5 In addition, conduit means 7 connect:

the exhaust space, consisting of that portion of the chamber formed in the cylinder head I0 ofcylinder 1 which is located between the exhaust valve 11 and the nozzle 4 and the intake space, consisting of that portion of the chamber in the cylinder head l0 of cylinder 1, which is comprised between the nozzle 6 and the intake valve 12,.

Due to this arrangement and as will appear on FIG. 3, where pressure p is plotted against volume v, one can see that:

immediately after opening of the exhaust valve 11 (point A) the pressure p in the cylinder 1 drops suddenly to a value lower than below the external or atmospheric pressure (part AB of the diagram) due to the fact that initial flow is supersonic (the pressure at A being more than twice the external pressure). Underpressure in the exhaust space of the cylinder 1 results from the kinetic energy of the slug expelled at high speed through the nozzle 4 The underpressure in the exhaust space of cylinder 1 maintains until the piston is close to the bottom dead center, due to the nozzle which opposes the return of the greater part of the expelled gases which constitute the first puff;

the pressure in cylinder 1 later builds up slightly above the external pressure and remains at such a pressure during the whole duration of the exhaust stroke BO.

Due to the communication provided by conduit 7 between the exhaust space of cylinder 1 and the intake space of cylinder 1,, the underpressure created in the exhaust space is transmitted with a slight delay to the intake space of the cylinder 1,, through the terminal ports 13 of the passage 7, which has the result of accelerating the feed of fresh gases into the passage 5, (fuel-air mixture from the carburetter manifold or air from the atmosphere, if the engine operates in a Diesel cycle).

At this moment, the piston of the cylinder 1 is close to its bottom dead center and its aspirating action ceases whilst, due to the improvement according to the invention, the aspiration is prolonged by the underpressure which is transmitted by the communication passage 7. This supplementary action increases the speed at which the gases are fed and consequently results in an increased pressure in the cylinder 1 until the moment of retarded closing of the intake valve 12 (R F A on FIG. 2) and this due to both the non-return action exerted by the nozzle 6 and to the slight increase in pressure in the exhaust space of the cylinder 1 Of course, there is provided a similar communication between the exhaust space of the cylinder 1 and the intake space of cylinder 1 (not shown in FIG. 1, for more clarity).

According to another feature of the invention, back flow of the exhaust gases from one cylinder towards the intake of the other cylinder, during the period which follows immediately the opening of the ports of the said exhaust, is avoided by interposing, as shown in FIG. 1, a non-retum nozzle 14 in each communication conduit 7.

It will be noted that the supercharging pressure is all the greater as the volume of the intake space is smaller. In the embodiment of the invention shown in FIGS. 4a, 4b, 40, a distributor separates the intake space 10 and the conduit 7. The distributor can be a slide valve comprising two bearing surfaces 15 and 16 connected by a rod 17 of lesser diameter, and adapted to control communication between space 10, and the opening 19 of the conduit 7 into a cylindrical bore or chamber 18 formed in the intake cylinder head 10. The bearing surfaces 15 and 16 are slidably mounted in chamber 18 to provide and to interrupt, at the desired moments, a communication established through the conduit 7 between the exhaust space of one cylinder and the intake space of the other cylinder. For this purpose, the movements of such slide valves l5, l6, 17 are time-related with the movements of the conventional distributing members, such as the intake valves. In the embodiment of FIG. 4a, the bearing surfaces 15 and 16 are formed on bulged portions of the rods of the intake valve 12 There has been shown in FIGS. 40, 4b, 40 three positions of the slide valve 15-16 with respect to the inner wall of the cylinder head 10, and with respect to the port 19, corresponding to three positions of the valve 12 It is seen that, in the position of FIG. 4a, which corresponds to the maximum lift of the said valve 12 the bearing surface 15 keeps port 19 closed. As the valve 12 moves upward towards its sealed position, the slide valve 15-16 first opens a communication between the conduit 7 and the intake space 10, (FIG. 4b) and latter cuts off communication when in the position of the FIG. 4c, before the valve 12, closes.

It is during the short period when communication is established through the slide valve 15-16 that the maximal underpressure in the exhaust space of the cylinder 1 produces a strong aspirating effect in the intake space of the cylinder head 10,. With a slight retard this results in a rise in pressure in the intake space, during the period when both pistons are in the vicinity of their bottom dead center. The intake space is then sealed off during the compression stroke of the piston in the cylinder 1,, firstly by the slide valve -16, secondly by the non-return nozzle 6, arranged in the intake passage 5,.

The non-return nozzles such as 4 may be of a type including an element having an aerodynamical shape and retained axially in bulged portions of the exhaust ports 3 and 3 Such elements are located in the flow of hot exhaust gas and act as heat accumulators. If the conduit 7 is located as indicated on FIG. 1, it directs onto the axial element an additional flow of a mixture consisting of fuel and excess air and it is found that the residual combustible fractions burn in that excess air along with the additional fuel delivered by the conduit 7.

Although this explanation should not be considered as certain, there is a strong probability that the substantial decrease in the pollution which has been noted is at least partially due to the eddies which occur when the mixture containing excess air is mixed with the exhaust gases and to the eddies which are evolved on those portions of the nozzles such as 42 where nonreturn action occurs.

The non-return nozzles are preferably of a type improved over the prior art for increased efficiency and induce annular swirling zones, as shown in FIGS. 5a and 5b, on the return path of the gases. Rotation is caused by inclined fins 20, formed in the toroidal cavity 32 of an axial mushroom-shaped element 21. The element 21 is preferably screwed on a threaded rod 23, so that the corss-section offered to flow at 22 may be adjusted by screwing the mushroom element 21 more or less deeply on its rod 23.

A ring 25 is retained in the outer wall close to the restricted section 22 and is provided with fins 26 cut in a direction opposite to that of the fins 20. It is seen that the gases in returning in the direction of the arrow form in the toroidal cavity of the mushroom element 21 a swirling ring, to which the fins 20 impart a rotary motion and which exerts a sealing effect. On the dislocation of the said swirling or vortex ring, the fins 26 impart to the dislocated swirls a reverse rotation creating a strong turbulence in the throttle section 22, which turbulence again opposes the return passage of the fluid after dislocation of the gaseous sealing rings.

Streams of fluid deviated from 27 to 27"by the toric cavity 32 and placed in rotation create turbulent streams which, by shock with the initial jets 28 guided by the part 30, considerably impede return of the gases in the output zone 29.

The outer jets or streams 28 guided by the wall 30 are deviated by the action of a circular crest or edge 31, adapted to rotate the said jets 28, in the same direction as the axial jets or.streams 27 which are induced to rotate in the toric cavity 32. The result of this arrangement is the formation of a continuous vortex ring 34 whose rotation, ensured around its axis by the fins 20, improves the stability and the obturating property to be obtained. 4

Although the invention has been described as embodied in a four-stroke engine with two opposed cylinders, it is obviously applicable to other engines comprising an even number of cylinders, which are grouped in pairs, each pair consisting of two cylinders having their times of operation out of phase by a half-period of a cycle. This is the case with two cylinder in line engines. With four cylinder in line engines and with the cylinders numbered 1 2 3 4 operating in the phase order 1 3 4 2, the conjugate pairs of cylinders are cylinders 1 4 and 2 3, the pistons in each group moving in phase and being operationally out of phase by a half-period of a complete cycle. In the case of six cylinder in line, numbered 1 2 3 4 5 6 and operating in the phase order 1 5 3 6 2 4, thepairs of selected conjugated cylinders to which the invention is applied are 1-6, 34, 2-5. In the same way, in eight cylinders in line engines operating in the phase order 1 6 2 8 4 7 3 5, the pairs of conjugate cylinders are respectively 14, 5-8, 2-3, 6-7. The same methods apply also to engines comprising several lines of cylinders disposed in V, in W or in X arrangements of which the conjugate cylinders in each pair are always selected out of phase by a half-period.

The invention is applicable to all multicylinder fourstroke heat engines, with any even number of cylinders, whatever their method of combustion, by carburation (particularly engines operating on a Otto cycle) or by injection, the nature of their fuels (liquid and gaseous petroleum products, light and heavy, rich and poor in gas) and whatever the uses which are made of the engines (terrestrial, maritime and aerial locomotion) and more particularly to engines of automobile vehicles, as well as to stationary engines whatever their use (electric generation, motors, compressor-motors, etc.).

Referring now to FIG. 6, there is shown a four-stroke flat twin engine similar to that of FIG. 1, which comprises two cylinders 101 and 102. Each cylinder locates a reciprocating piston 103. Each piston is coupled by a rod to a crankshaft having two cranks. Each cylinder is provided with an intake valve 104 and an exhaust valve 105 controlled by cams in such a way that the two cylinders operate in succession with a time interval corresponding to a half-period, that is with an angular offset of 360.

The cylinders are fed by a carburetter 106 which delivers an air-fuel combustible mixture via a pipe 108 which opens into the intake space 107 of each cylinder.

As in the embodiment of FIG. 1, an aerodynamical non-return nozzle is located between the exhaust space 1 10 of each cylinder and the exhaust pipe 110a and includes an axial element 111. A pipe 112 provides a gas path between the intake space of each cylinder and the exhaust space of the other cylinder. Last, an aerodynamical non-return nozzle is located between each intake pipe 108 and the intake space 107 of the corresponding cylinder, close to the location where the communication pipe 112 opens into the intake space of the corresponding cylinder, thereby preventing substantial flow of exhaust gases from the associated cylinder back towards the intake space from occurring.

In order to ensure complete combustion of the combustible fractions (carbon monoxide and unbumt hydrocarbons) which are still present in the exhaust gases and which are responsible for a substantial portion of atmospheric pollution, there is included in each exhaust pipe an element which has a substantial heat capacity, stores a large amount of heat when subjected to the flow of exhaust gases and burns the pollutants. A flow of a mixture containing fuel and air in more than stoechiometric proportion is directed onto that element so that the polluting elements which are in the exhaust gases are burnt when in the vicinity of the heat storing element or in contact therewith, due to the fact that the exhaust gases and the comburant gas (oxygen from air) contact that element at the same time.

As indicated above with reference to FIG. 1, the

heat-storing elements may preferably consist each of the axial element 111 of the non-return nozzle 109 which is located in the corresponding exhaust pipe. For this purpose the axial element is given a bulk and weight sufficient for it to store the heat necessary for said combustion to occur. In addition, the communication pipe which opens in front of the axial element is used to direct additional air (used as a comburant). For this purpose, one or several air inlets 115 are provided in the terminal part of the communication pipe close to the opening into exhaust space 110.

For more efficient combustion of the pollutants of the exhaust gases, a small fraction of the air-fuel mixture which flows towards the cylinder which is being fed is preferably by-passed towards the exhaust space 110 and mixed with the air which is drawn through the inlet 115. The rate at which the fuel mixture with the air is introduced should be such that the fuel is completely burnt.

Means are preferably provided for controlling the rate of air flow which is admitted via the inlet or inlets 115 into the exhaust space 110. Referring to FIG. 8, an annular housing 116 is secured onto the pipe and surrounds that portion where the inlets 115 are formed. Openings 117 are formed in the housing 116 and a sleeve 118 formed with openings adapted to register with the openings 117 is slidably mounted for rotation on the housing. Upon rotation of the sleeve 118, the openings 119 and 1 17 have different amount of overlap and the inlet section is altered. The sleeve 118 may be controlled by a mechanism which also determines the amount of fuel which is fed to the engine. In automotive vehicles, the treadle which controls the throttle valve (gasoline engine) or the injunction pump (Diesel engine) will be used.

In the arrangement illustrated on FIG. 8, a cable 120 is connected to a radial lug of sleeve 118 for rotating the sleeve in the direction which tends to throttle opening 117. The cable provides a non-positive connection and the sleeve 118 is biased in a direction which tends to uncover opening 117 by a spring 121 located in a stationary housing. The spring is compressed between the bottom wall of the housing and a piston 124 whose rod 123 is pivotably connected to a projection of sleeve 118. The piston and housing constitute a dash-pot provided with a ball valve which renders it ineffective when the sleeve is actuated to close the opening 117. On the contrary, the dash-pot counteracts rapid uncovering of the opening 117. The extent to which the openings 117 may be uncovered is adjustable by means of a stop member 125, which may be a threaded member screwed in a stationary part.

The control mechanism of FIG. 8 makes it possible to obtain maximum power when necessary (during accelerations and up-hill driving), that is during short time periods at the cost of a temporary suppression of the otherwise obtained decrease of the amount of pollution: at such time the opening 117 is throttled or closed and this results in partial or complete suppression of the additional air-flow. On the contrary, under normal driving conditions the rate of flow is determined by the stop member 125, adjusted for maximum anti-pollution effect.

Fox-maximum heat-storing action of the heat-storing element 111, thermal insulation means may be located between said element and its support 129. As shown in FIG. 7, such means may consist of a sleeve 126 and washers 127 and 128 of insulating material. This arrangement makes it possible to maintain element 111 at a high temperature at all times during the three stokes other than the exhaust strokes.

For maximum anti-polluting action, part at least of the surface of element 111 may be formed or coated with a catalyst selected for complete oxidation of hydrocarbons without flame. In the embodiment illustrated on FIG. 7, the head of the axial element of the non-return nozzle is coated with an annular layer of such catalyst.

In the embodiment of FIG. 7, a spring-loaded nonreturn poppet valve 131 is located in the communication pipe 112, downstream of the aerodynamical nonreturn nozzle 114. The poppet valve 131 cooperates with the non-return nozzle 114 in avoiding significant backflow of exhaust gases toward the communication pipe and the intake space 107 of that cylinder which is being fed by the carburetter 106. The poppet-valve exerts an action which relays that of the nozzle during operation at idle speed and during start-up while the nozzle is unefficient and would not prevent the gases from flowing back.

Since the action of the nozzle should be complemented at low speed only, the weight of the non-return valve 131 and the bias force exerted by the return spring 132 are so selected that under normal operation the poppet-valve does not close again during an engine cycle after it has been opened once by the underpressure resulting from a first exhaust puff.

According to still another feature of the invention, a deflector vane 133 (FIG. 7) may be provided at such a location that it deflects the air-rich gas mixture flowing from pipe 112 and directs it onto the head of the heat storing part 111 at an optimum incidence angle. The deflector vane also ensures satisfactory repartition of the inflow onto the head and protects the poppetvalve 131 and the return spring 132 against the hot exhaust gases. In the embodiment illustrated on FIG. 7, the deflector vane 133 is secured on the support 134 in which the stem of the poppet-valve 131 is slidably received.

While the embodiments of FIGS. 1 5 and 6 8 relate to a four-stroke two-cylinder reciprocal piston engine, FIGS. 9 10 illustrate a rotary piston engine which constitutes another embodiment. Referring to FIGS. 9 and 10, there is shown a rotary piston engine which is generally known in the art as a Wankel engine. Although the illustrated engine has two rotors, it should be understood that the invention may be used with any Wankel engine having an even number of rotors. The two triangular rotors of the engine of FIG. 9 belong to the sub-assemblies A and B. The two rotors drive a shaft 135. Each rotor consists of a prismatic part, respectively referred to as 136 and 137, having a curvilinear, triangular cross-section. Each prismatic part is simultaneously moved in rotation and in translation since its inner toothed ring 138 meshes with a lower diameter pinion 139 which is secured on shaft 135. Each prismatic portion moves in such a way that the edges at the three apices of the triangle sealingly slide on the surface ofa chamber 140 formed in a housing 141. Chamber 140 has a two-lobed epitrocoidal ties between the wall of chamber 40 and each of the lateral surfaces of the prismatic rotoris modifed fourtimes during a period (two increases and two decreases). These variations correspond to the four strokes of conventional reciprocal piston engines. Intake and exhaust action is by the rotor itself whose apices cooperate with stationary ports 142 and 143 formed in the housing. The two prismatic rotors are so located angularly with respect of each other that their strokes are offset by a half-period of a complete cycle. In the embodiment illustrated on FIGS. 9 and 10, the two rotors rotate in the direction of arrow f. When rotor 136 initially uncovers the exhaust port 143 of sub-assembly B, the rotor 137 has not yet closed the intake port 142 of sub-assembly'A. Consequently the situation is the same as that which occurs in a multicylinder alternating piston engine. Further description of the Wankel engine is deemed useless since construction and operation thereof are well known to those skilled in the art.

According to the invention, the intake space 144 corresponding to rotor 137 of sub-assembly A is communicated with the exhaust space 145 corresponding to rotor 136 (sub-assembly B) by duct means 146, 147, 148 which corresponds to the communication pipe 112 of FIGS. 6 and 7 and FIG. I. Duct means 146, 147 and 148 opens into the exhaust space in front of the head of the axial element 149 of a non-return nozzle located in the exhaust space 145. The duct portion 147 is provided with a port 150 for admission of a comburant gas (which will generally be air drawn from atmosphere). The rate of flow in port 150 is adjustable by means which are schematically illustrated on FIG. 9 as a throttle valve 151. The duct means 146, 147, 148 also locates a non-return valve 152 whose weight and return spring are arranged and proportioned as those of valve 131 of FIG. 7. A non-return nozzle 153 is located in the intake port in series relation with the non-return valve thereof. Such an arrangement results in increased yields and reduced pollution as indicated above with respect to FIGS. 1 8.

It should be noted that narrow slots are preferably cut in the chamber wall for providing a restricted flow communication between the intake duct and the chamber just before the rotor uncovers the main portion of the intake port 143 and between the exhaust space and the chamber for a short time after the rotor has closed the main portion of the exhaust port 142, at least if supercharging is to be obtained. On FIG. 9, each slot is of triangular shape and has a circumferential length which is about the same as that of the main portion.

I claim:

1. A method for supercharging a multicylinder fourstroke internal combustion engine having at least one pair of cylinders, comprising using the under pressure which prevails in the exhaust space of each of the cylinders immediately following the first exhaustdischarge for drawing fresh gas into the intake space of the other cylinder of the same pair.

2. The method for supercharging an engine of claim I, wherein the engine operative means within the cylinders of the pair of cylinders are out of phase with respect to each other by a half cycle.

3. A method of operating a multi-cylinder reciprocating piston four stroke internal combustion engine, comprising communicating the exhaust space of each cylinder with the intake space of another cylinder which is out of phase with the first named cylinder by half a cycle for part at least of the time period of each cycle which extends from opening of the intake of the first named cylinder to closing of the exhaust of the second named cylinder and substantially preventing back flow from said exhaust space to said intake space.

4. In a multicylinder four-stroke internal combustion engine, the improvement comprising individual respective passage means communicating the exhaust space of each cylinder of the engine with the intake space of a second cylinder of the engine which is out of phase by a half-cycle period with respect to the first-named cylinder, non-return means located in the exhaust space of the first-named cylinder, and additional nonretum means in said passage means for restricting reverse flow from the exhaust space to the intake space.

5. A multicylinder four stroke internal combustion engine according to claim 4, having at least one pair of cylinders and one rotor in each cylinder, wherein the intake space of each cylinder cooperates with the exhaust space of the other cylinder of the same pair.

6. A multicylinder four stroke internal combustion engine according to claim 4, wherein each said cylinder of a pair of communicating cylinders has within it means which operates within the. cylinder for moving through the four strokes of the internal combustion engine, and it is these said means in the pair of cylinders which are out of phase with respect to each other by a half cycle.

7. Engine according to claim 4, having non-return means located, in the intake space of the secondnamed cylinder upstream of the position where said passage means opens into said intake space.

8. Engine according to claim 4, wherein each said non-return means comprises an aerodynamic nozzle which impresses a head loss to back flow much in excess to that to forward flow.

9. Engine according to claim 4, having control means for periodically establishing and interrupting communication between the exhaust space of the first-named cylinder and the intake space of the second-named cylinder.

10. Engine according to claim 9, wherein said control means are operatively connected to one at least of the intake valves and exhaust valves of said cylinders.

11. Engine according to claim 8, wherein each nonretum nozzle comprises walls limiting an annular cavity located in the path of the gas, opposite to normal flow thereof and provided with inclined fins which cause rotation of return gas around the axis of said nozzle.

12. Engine according to claim 11, wherein said inclined fins constitute an inner group of fins inclined in a first direction and an outer group of fins inclined in reverse direction and surrounding the inner group, said two groups limiting an annular passage for direct flow of the exhaust gases.

13. Engine according to claim 7, including control means which establish and interrupt periodically one at least the communications between the exhaust space of the first cylinder and the intake space of the second cyl- 14. A multicylinder four-stroke internal combustion engine having an even number of cylinders each having spaces, each'of said cylinders being operated out of phase with another of said cylinders by half a complete four-stroke cycle, the improvement consisting of means for providing a substantially one-way communication from the intake space of each said cylinder to the exhaust space of another cylinder which is out of phase with the first by half a cycle.

15. An engine according to claim 14, having a heat storing element located in each said exhaust space for being swept by exhaust gases at a temperature close to the temperature at which they flow out of the corresponding cylinder, an outlet for said communication means into each said exhaust space so constructed and arranged that the gases flowing along said means are directed onto said element and means for controlling the air content of the gases delivered at said mouth.

16. An engine according to claim 15, having an exhaust pipe for each cylinder and aerodynamical nonreturn means for the exhaust gases in each said exhaust space, said non-return means comprising an element located axially with said exhaust pipe and which constitutes said heat storing element.

17. An engine according to claim 15, having a combustion catalyst on said heat storing element.

18. An engine according to claim 15, having heat insulating support means for said heat storing element.

19. An engine according to claim 14, having nonreturn means in each said exhaust space, said means comprising an aerodynamically shaped element retained within said exhaust space and cooperating therewith to oppose back flow of exhaust gases toward the corresponding cylinder, and air inlet means in each said communication means, each said communication means being constructed to direct the gas flowing therethrough toward said element.

20. An engine according to claim 19, having throttle means for controlling the air flow through said inlet means.

21. An engine according to claim 20, having means for controlling the amount of fuel fed to said engine, wherein said throttle means are operatively connected with said control means.

22. An engine according to claim 21, having a oneway connection between said throttle means and control means for positive actuation of said throttle means toward closure of the air flow, resilient return means for said throttle means, and dash pot means opposing a force to action of said return means to delay increase of said air flow by said resilient means.

23. An engine according to claim 14, wherein said communication means includes a pipe for each exhaust space, aerodynamical non-return means in said pipe, and a non-return valve located in series relation with said aerodynamical means, said return valve being so arranged that it remains open throughout complete cycles when the speed of the engine exceeds a predetermined value.

24. An engine according to claim 23, wherein said valve is located close to said exhaust space and is provided with stationary deflector means which cooper ates in directing onto said element the gases flowing into said exhaust space.

25. In a multi-cylinder reciprocating piston four stroke internal combustion engine and the like having intake opening advance and exhaust closing retard, each cylinder having an intake space and an exhaust space separated from the cylinder by intake and exhaust valves, respectively, the improvement comprising, for each cylinder of the engine:

passage means communicating the exhaust space of said cylinder with the intake space of another cylinder which is out of phase by a half-cycle with respect to the first-named cylinder,

non-return means in the exhaust space of said cylinder for preventing back flow of exhaust gases toward said cylinder,

flow control means in said passage means for permitting flow in said passage means from the intake space of said cylinder while substantially preventing back flow toward said intake space. 

1. A method for supercharging a multicylinder four-stroke internal combustion engine having at least one pair of cylinders, comprising using the under pressure which prevails in the exhaust space of each of the cylinders immediately following the first exhaust discharge for drawing fresh gas into the intake space of the other cylinder of the same pair.
 2. The method for supercharging an engine of claim 1, wherein the engine operative means within the cylinders of the pair of cylinders are out of phase with respect to each other by a half cycle.
 3. A method of operating a multi-cylinder reciprocating piston four stroke internal combustion engine, comprising communicating the exhaust space of each cylinder with the intake space of another cylinder which is out of phase with the first named cylinder by half a cycle for part at least of the time period of each cycle which extends from opening of the intake of the first named cylinder to closing of the exhaust of the second named cylinder and substantially preventing back flow from said exhaust space to said intake space.
 4. In a multicylinder four-stroke internal combustion engine, the improvement comprising individual respective passage means communicating the exhaust space of each cylinder of the engine with the intake space of a second cylinder of the engine which is out of phase by a half-cycle period with respect to the first-named cylinder, non-return means located in the exhaust space of the first-named cylinder, and additional non-return means in said passage means for restricting reverse flow from the exhaust space to the intake space.
 5. A multicylinder four stroke internal combustion engine according to claim 4, having at least one pair of cylinders and one rotor in each cylinder, wherein the intake space of each cylinder cooperates with the exhaust space of the other cylinder of the same pair.
 6. A multicylinder four stroke internal combustion engine according to claim 4, wherein each said cylinder of a pair of communicating cylinders has within it means which operates within the cylinder for moving through the four strokes of the internal combustion engine, and it is these said means in the pair of cylinders which are out of phase with respect to each other by a half cycle.
 7. Engine according to claim 4, having non-return means located, in the intake space of the second-named cylinder upstream of the position where said passage means opens into said intake space.
 8. Engine according to claim 4, wherein each said non-return means comprises an aerodynamic nozzle which impresses a head loss to back flow much in excess to that to forward flow.
 9. Engine according to claim 4, having control means for periodically establishing and interrupting communication between the exhaust space of the first-named cylinder and the intake space of the second-named cylinder.
 10. Engine according to claim 9, wherein said control means are operatively connected to one at least of the intake valves and exhaust valves of said cylinders.
 11. Engine according to claim 8, wherein each non-return nozzle comprises walls limiting an annular cavity located in the path of the gas, opposite to normal flow thereof and provided with inclined fins which cause rotation of return gas around the axis of said nozzle.
 12. Engine according to claim 11, wherein said inclined fins constitute an inner group of fins iNclined in a first direction and an outer group of fins inclined in reverse direction and surrounding the inner group, said two groups limiting an annular passage for direct flow of the exhaust gases.
 13. Engine according to claim 7, including control means which establish and interrupt periodically one at least the communications between the exhaust space of the first cylinder and the intake space of the second cylinder and between the exhaust space of the first cylinder and the intake space of the second cylinder.
 14. A multicylinder four-stroke internal combustion engine having an even number of cylinders each having an intake space, an exhaust space and means for controlling communication between said cylinder and said spaces, each of said cylinders being operated out of phase with another of said cylinders by half a complete four-stroke cycle, the improvement consisting of means for providing a substantially one-way communication from the intake space of each said cylinder to the exhaust space of another cylinder which is out of phase with the first by half a cycle.
 15. An engine according to claim 14, having a heat storing element located in each said exhaust space for being swept by exhaust gases at a temperature close to the temperature at which they flow out of the corresponding cylinder, an outlet for said communication means into each said exhaust space so constructed and arranged that the gases flowing along said means are directed onto said element and means for controlling the air content of the gases delivered at said mouth.
 16. An engine according to claim 15, having an exhaust pipe for each cylinder and aerodynamical non-return means for the exhaust gases in each said exhaust space, said non-return means comprising an element located axially with said exhaust pipe and which constitutes said heat storing element.
 17. An engine according to claim 15, having a combustion catalyst on said heat storing element.
 18. An engine according to claim 15, having heat insulating support means for said heat storing element.
 19. An engine according to claim 14, having non-return means in each said exhaust space, said means comprising an aerodynamically shaped element retained within said exhaust space and cooperating therewith to oppose back flow of exhaust gases toward the corresponding cylinder, and air inlet means in each said communication means, each said communication means being constructed to direct the gas flowing therethrough toward said element.
 20. An engine according to claim 19, having throttle means for controlling the air flow through said inlet means.
 21. An engine according to claim 20, having means for controlling the amount of fuel fed to said engine, wherein said throttle means are operatively connected with said control means.
 22. An engine according to claim 21, having a one-way connection between said throttle means and control means for positive actuation of said throttle means toward closure of the air flow, resilient return means for said throttle means, and dash pot means opposing a force to action of said return means to delay increase of said air flow by said resilient means.
 23. An engine according to claim 14, wherein said communication means includes a pipe for each exhaust space, aerodynamical non-return means in said pipe, and a non-return valve located in series relation with said aerodynamical means, said return valve being so arranged that it remains open throughout complete cycles when the speed of the engine exceeds a predetermined value.
 24. An engine according to claim 23, wherein said valve is located close to said exhaust space and is provided with stationary deflector means which cooperates in directing onto said element the gases flowing into said exhaust space.
 25. In a multi-cylinder reciprocating piston four stroke internal combustion engine and the like having intake opening advance and exhaust closing retard, each cylinder having an intake space and an exhaust space separated from the Cylinder by intake and exhaust valves, respectively, the improvement comprising, for each cylinder of the engine: passage means communicating the exhaust space of said cylinder with the intake space of another cylinder which is out of phase by a half-cycle with respect to the first-named cylinder, non-return means in the exhaust space of said cylinder for preventing back flow of exhaust gases toward said cylinder, flow control means in said passage means for permitting flow in said passage means from the intake space of said cylinder while substantially preventing back flow toward said intake space. 